haskell - Cabal 未安装 4.7.0.0 版本的 base

Question

我需要 Data.Either v. 4.7.0.0 的新函数“isLeft”，但 cabal 没有安装新库。

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Users\Alberto>cabal update
Downloading the latest package list from hackage.haskell.org
Note: there is a new version of cabal-install available.
To upgrade, run: cabal install cabal-install

C:\Users\Alberto>cabal install base
Resolving dependencies...
All the requested packages are already installed:
base-4.6.0.1
Use --reinstall if you want to reinstall anyway.

C:\Users\Alberto>date
The current date is: 19/04/2014

为什么会发生这种情况？

如何将基础包升级到版本 4.7？

Answer 1

base 是一个特殊的包。您无法升级它。如果您想要 base-4.7，则必须使用 GHC 7.8。